1. Field of the Invention
The present invention relates to a recording apparatus for performing the recording operation of a sheet member conveyed by a conveying means using a recording means.
2. Related Background Art
In an image forming apparatus using a conventional ink jet system, an image designated on a sheet of recording paper is generally reproduced as an ink image by cooperatively performing an operation for conveying the recording paper sheet in a subscanning direction, discharging control of a recording head for discharging ink to the recording paper sheet, and an operation for reciprocating the recording head in a main scanning direction (a direction perpendicular to the subscanning direction).
When the distance between a paper face and the recording head is excessively widened, the accuracy of an attaching position of an ink droplet discharged from the recording head is reduced so that the image is disturbed. Therefore, this distance is shortened as much as possible. However, in the ink jet recording system, the image is formed by discharging the ink having water as a main component to paper. Therefore, the paper is expanded and irregular xe2x80x9cwrinklesxe2x80x9d are caused. The paper face approaches the recording head by these xe2x80x9cwrinklesxe2x80x9d so that the paper face is rubbed by the recording head and the image is disturbed.
Therefore, a recording apparatus having an irregularity forming discharging portion as a means for controlling a generating degree of the xe2x80x9cwrinklesxe2x80x9d in the recording paper sheet is already proposed as a countermeasure for the rubbing of the recording paper sheet and the recording head caused by the generation of xe2x80x9cwrinklesxe2x80x9d in the recording paper sheet.
FIG. 10 is a cross-sectional view showing the irregularity forming discharging portion in the conventional recording apparatus.
As shown in FIG. 10, the irregularity forming discharging portion in the conventional recording apparatus is constructed by a conveying roller 101, a pinch roller 102, a platen 104 and a paper discharging roller 105. The conveying roller 101 conveys a recording paper sheet S to a portion below an ink discharging portion of the recording head 103. The pinch roller 102 is rotated by the conveying roller 101 and presses against the conveying roller 101 and presses the recording paper sheet S against the conveying roller 101. The platen 104 is opposed to the recording head 103 and supports the recording paper sheet S. The paper discharging roller 105 discharges the recording paper sheet S after printing.
Plural ribs 104a are arranged at an interval from 20 to 30 mm in the irregularity forming discharging portion of the platen 104. The recording paper sheet S is supported on an upper face of each of these ribs 104a. A height of each rib 104a is set such that the gas between the recording head 103 and the recording paper sheet S supported on the upper face of the rib 104a is minimized. A portion of the rib 104a opposed to the recording head 103 is arranged in parallel with the ink discharging portion of the recording head 103. An upstream side portion of the rib 104a in a conveying direction of the recording paper sheet in the vicinity of the conveying roller 101 is formed in a taper shape in which a height of this upstream side portion is gradually increased from a low position to the height of the upper face along the conveying direction of the recording paper sheet. In contrast to this, a portion of the platen 104 except for the rib 104a is formed such that the height of this portion is lower by about 2 mm than the upper face of the rib 104a. 
An axis of the pinch roller 102 is arranged in a position shifted by about 1 to 2 mm on a downstream side in the conveying direction from an axis of the conveying roller 101. Thus, an end tip of the conveyed recording paper sheet S hits against the taper portion of the rib 104a and the recording paper sheet S is then pressed against the upper face of the rib 104a. The paper discharging roller 105 is formed in a shape in which a rubber portion 105a coming in contact with the recording paper sheet S is divided in an axial direction of the paper discharging roller 105. Each rubber portion 105a is arranged in a position conforming to each rib 104a of the platen 104 in the conveying direction of the recording paper sheet S.
In accordance with the recording apparatus constructed above, the recording paper sheet S is conveyed while the recording paper sheet S is pressed against the upper face of the rib 104a. At this time, a portion of the recording paper sheet S not supported by the rib 104a is pushed into a slightly low portion between ribs 104a adjacent to each other. In this state, when ink is discharged from the recording head 103 to the recording paper sheet S, the recording paper sheet S is expanded by water of the ink so that an expanded portion further enters a low portion between the ribs 104a. As a result, a portion of the recording paper sheet S supported on the upper face of each rib 104a becomes xe2x80x9cconvexxe2x80x9d, and a portion of the recording paper sheet S between ribs 104a adjacent to each other becomes xe2x80x9cconcavexe2x80x9d. Namely, irregularities having a corrugated plate shape in the main scanning direction are formed in the recording paper sheet S to which the ink is discharged. At this time, the gap between the recording paper sheet S and the recording head 103 is minimized in a portion (convex portion) supported on the upper face of the rib 104a. Accordingly, it is possible to prevent the paper face S and the recording head 103 from being rubbed. Thus, the recorded recording paper sheet S is conveyed and discharged outside the recording apparatus. The above irregularities are not formed in the subscanning direction in the recording paper sheet S recorded by discharging the ink.
As mentioned above, the height of each rib 104a is set such that the gas between the recording head 103 and the recording paper sheet S supported on the upper face of the rib 104a is minimized. Thus, dispersion in a gap difference of the irregularities of the recording paper sheet S can be set to lie within the range of an allowing gap amount at a time of the ink discharging operation of the recording head 103 so that a preferable image can be formed.
A fixing time of the ink to the paper face is required to form the image by discharging the ink to the paper face. However, when a printing speed of the recording apparatus is increased, the next recording paper sheet is discharged before the ink is fixed to the printed recording paper sheet discharged to the discharging portion. Accordingly, an end tip or a rear face of a subsequent recording paper sheet rubs an ink image of the recording paper sheet already discharged so that there is a fear of image disturbance.
Therefore, another recording apparatus is conventionally proposed. In this recording apparatus, a supporting member for supporting both ends of the subsequent recording paper sheet is arranged to prevent the subsequent recording paper sheet from being rubbed by the recording paper sheet already discharged to the discharging portion while the printed recording paper sheet is conveyed and the subsequent recording paper sheet is printed. Fixation of the ink to the recording paper sheet already discharged to the discharging portion is completed by natural drying while an image is printed on the subsequent recording paper sheet. Thus, the subsequent recording paper sheet can be discharged onto the recording paper sheet already discharged.
FIG. 11 is a cross-sectional view showing another conventional recording apparatus. FIG. 12 is a perspective view showing a supporting member in the conventional recording apparatus shown in FIG. 11.
As shown in FIG. 11, the conventional another recording apparatus is constructed such that a recording paper sheet fed by a paper feed means 111 is conveyed by a conveying portion 112 to a portion below a recording head 113 and is recorded, and is then stacked by a paper discharging roller 114 on a paper discharging tray 115. Further, in this conventional recording apparatus, a supporting member 116 for supporting the conveyed recording paper sheet S is arranged on a downstream side of the paper discharging roller 114 with respect to a conveying direction of the recording paper sheet S.
As shown in FIG. 12, the supporting member 116 supports the rear side of a printing face of the recording paper sheet S by a rib 116a in a position corresponding to an approximately entire width. At this time, the recording paper sheet S is flexed in a concave shape by the rib 116a supporting each of both side end portions of the recording paper sheet S so that xe2x80x9cfirmnessxe2x80x9d for preventing downward bending of an end tip portion of the recording paper sheet S is given to this recording paper sheet. Therefore, the recording paper sheet S is held in the air as shown in FIG. 12 until a rear end portion of the recording paper sheet S passes through the supporting member 116. Accordingly, while the recording paper sheet S is printed and is discharged and conveyed, the supporting member 116 holds the recording paper sheet S such that this recording paper sheet S is not rubbed by the recording paper sheet S already discharged to the paper discharging tray 115.
In this conventional recording apparatus, the ink of the recording paper sheet S already discharged onto the discharging tray 115 is naturally dried to secure an ink fixing time of the recording paper sheet S while a subsequent recording paper sheet S is printed.
When the subsequent recording paper sheet S is discharged onto the paper discharging tray 115, the supporting member 116 is rotated around an axis perpendicular to the conveying direction of the recording paper sheet S as a center and is escaped to a portion below the paper discharging roller 114 when a rear end of the recording paper sheet S reaches the paper discharging roller 114. An escaping operation of the supporting member 116 is associated with a conveying operation of the paper discharging roller 114. Accordingly, while the paper discharging roller 114 discharges the recording paper sheet S, the supporting member 116 is escaped as mentioned above.
Thus, in accordance with this conventional recording apparatus, the subsequent recording paper sheet S is stacked onto the recording paper sheet S already discharged onto the discharging tray 115 and naturally dried. Accordingly, no subsequent recording paper sheet S rubs an unfixed ink image so that disturbance of the recorded image is prevented.
However, when a recording apparatus is constructed by combining the irregularity forming discharging portion and the supporting member of the above-mentioned two recording apparatuss and the supporting member is simply arranged on a downstream side in the conveying direction from the irregularity forming discharging portion, the irregularities of a corrugated plate shape formed in the recording paper sheet by the irregularity forming discharging portion are broken by the supporting member. As a result, the gap between the recording head and the recording paper sheet is reduced in a portion to be xe2x80x9cconcavexe2x80x9d rather than a portion to be xe2x80x9cconvexxe2x80x9d in a position opposed to the recording head.
Here, this phenomenon will be explained with reference to FIG. 13.
FIG. 13 is a plan view showing a recording paper sheet conveying portion in the recording apparatus constructed by combining respective characterizing portions of the above conventional two recording apparatuss. In this recording apparatus, a supporting member 216 having a rib 216a is arranged on a downstream side in the conveying direction from a platen having a rib 204a. The constructions of a conveying roller 201, a pinch roller 202, the rib 204a arranged on the unillustrated platen, a paper discharging roller 205 and a rubber portion 205a in the recording apparatus shown in FIG. 13 are similar to those in the recording apparatus shown in FIG. 10. Constructions of the supporting member 216 and the rib 216a are similar to those in the recording apparatus shown in FIGS. 11 and 12. Accordingly, detailed explanations of these constructions are omitted here.
In the recording apparatus shown in FIG. 13, the rib 204a on the platen and the rubber portion 205a of the paper discharging roller 205 are arranged at an interval of 30 mm (15, 45, 75, 105, 135, 165 and 195 mm from a left-hand end) from a position of 15 mm from a left-hand end of the recording paper sheet S so as to convey the recording paper sheet of an A4 size. In this case, each of portions shown by one-dotted chain lines a to g in FIG. 13 is a portion to be xe2x80x9cconvexxe2x80x9d. Each of portions shown by two-dotted chain lines h to m in FIG. 13 is a portion to be xe2x80x9cconcavexe2x80x9d.
However, for example, when the rib 216a of the supporting member 216 is arranged in a position separated by 5 mm from each of both side ends of the recording paper sheet S, a portion of the recording paper sheet S supported by each rib 216a becomes xe2x80x9cconvexxe2x80x9d. Therefore, in addition to the xe2x80x9cconvexxe2x80x9d of the above portions a to g, a convex portion is caused on each of lines n and o connecting each rib 216a and each rubber portion 205a at both ends of the paper discharging roller 205. Thus, portions p and q to be originally xe2x80x9cconcavexe2x80x9d become xe2x80x9cconvexxe2x80x9d and the recording paper sheet S is expanded by attaching the ink to this recording paper sheet. Accordingly, the portions p and q highly float and rise from portions of lines a to g to be originally xe2x80x9cconvexxe2x80x9d. Thus, a problem exists in that a printing face of the recording paper sheet comes in contact with the recording head.
An object of the present invention is to provide a recording apparatus which can prevent a sheet member from being rubbed by a recording means, and can prevent a recorded unfixed ink image from being rubbed and disturbed by a subsequent sheet member.
Another object of the present invention is to provide a recording apparatus for performing the recording operation of a recording medium conveyed by conveying means using recording means, said apparatus comprising: irregularity forming discharging means for forming said recording medium in a shape having corrugated irregularities in a direction crossing a conveying direction of the recording medium in a position of said recording medium opposed to said recording means, and discharging said recording medium to the exterior of said recording apparatus; and supporting means for supporting said recording medium discharged by said irregularity forming discharging means so as to curve the recording medium in a concave shape with respect to a direction perpendicular to said conveying direction, wherein the supporting means is arranged in a position corresponding to a convex portion near each of both end portions of the recording medium formed in the shape having said corrugated irregularities with respect to said conveying direction.
Another object of the present invention is to provide an image forming apparatus for discharging a sheet forming an image thereon to a discharging portion, said apparatus comprising: recording means having a carriage for moving a recording head in a width direction and a roller for conveying the sheet, and forming the image to the conveyed sheet; discharging means having a set of a first discharging roller constructed by a roller and a rotating body rotated by the roller on a downstream side in a sheet discharging direction from the recording means, and a set of a second discharging roller on a further downstream side; supporting means of a projecting shape arranged in the vicinity of both end portions of the discharged sheet in its width direction between the first and second discharging rollers of said discharging means in a conveying direction of the discharged sheet, or approximately in the same column as the second discharging roller set; and pushing-up means for biasing said supporting means from a second position to a first position by a resilient member such as a spring, and the like, wherein the supporting means is able to be moved to the first position for projecting the supporting means to a conveying path of said sheet and raising a face of said sheet on a side opposed to a recorded face of said sheet; and supporting the sheet by curving the sheet in a concave shape in the width direction of the sheet, and able to be also moved to the second position escaped from the conveying path of the sheet.